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std::try_lock

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Threads
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Threads
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thread(C++11)
this_thread namespace
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this_thread namespace
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get_id(C++11)
yield(C++11)
sleep_for(C++11)
sleep_until(C++11)
Exclusão mútua
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Mutual exclusion
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mutex(C++11)
timed_mutex(C++11)
Gestão de bloqueio genérico
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Generic lock management
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lock_guard(C++11)
unique_lock(C++11)
defer_lock_t
try_to_lock_t
adopt_lock_t
(C++11)
(C++11)
(C++11)
lock(C++11)
try_lock(C++11)
defer_lock
try_to_lock
adopt_lock
(C++11)
(C++11)
(C++11)
Variáveis ​​de condição
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Condition variables
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condition_variable(C++11)
condition_variable_any(C++11)
notify_all_at_thread_exit(C++11)
cv_status(C++11)
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Futures
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promise(C++11)
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packaged_task(C++11)
async(C++11)
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future_error(C++11)
future_category(C++11)
future_errc(C++11)
 
Defined in header <mutex>
template< class Lockable1, class Lockable2, class LockableN... >
int try_lock( Lockable1& lock1, Lockable2& lock2, LockableN& lockn... );
(a partir do C++ 11)
Tenta bloquear cada um dos objetos dado Lockable lock1, lock2, ..., lockn chamando try_lock no início ordem com o primeiro.
Original:
Tries to lock each of the given Lockable objects lock1, lock2, ..., lockn by calling try_lock in order beginning with the first.
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Se uma chamada para try_lock falhar, unlock é chamado por quaisquer objetos bloqueados e um índice baseado 0 do objeto que não conseguiu travar é devolvido.
Original:
If a call to try_lock fails, unlock is called for any locked objects and a 0-based index of the object that failed to lock is returned.
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Se uma chamada para resultados try_lock em uma exceção, unlock é chamado por quaisquer objetos bloqueados antes relançando.
Original:
If a call to try_lock results in an exception, unlock is called for any locked objects before rethrowing.
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Índice

[editar] Parâmetros

lock1, lock2, ... , lockn -
o Lockable objetos para bloquear
Original:
the Lockable objects to lock
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[editar] Valor de retorno

-1 em sucesso, ou valor de índice 0 baseado do objeto que não conseguiu travar.
Original:
-1 on success, or 0-based index value of the object that failed to lock.
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[editar] Exemplo

O exemplo a seguir usa std::try_lock periodicamente registro e contadores reiniciadas em execução em segmentos separados .
Original:
The following example uses std::try_lock to periodically tally and reset counters running in separate threads.
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#include <mutex>
#include <vector>
#include <thread>
#include <iostream>
#include <functional>
#include <chrono>
 
int main()
{
    int foo_count = 0;
    std::mutex foo_count_mutex;
    int bar_count = 0;
    std::mutex bar_count_mutex;
    int overall_count = 0;
    bool done = false;
    std::mutex done_mutex;
 
    auto increment = [](int &counter, std::mutex &m,  const char *desc) {
        for (int i = 0; i < 10; ++i) {
            std::unique_lock<std::mutex> lock(m);
            ++counter;
            std::cout << desc << ": " << counter << '\n';
            lock.unlock();
            std::this_thread::sleep_for(std::chrono::seconds(1));
        }
    };
 
    std::thread increment_foo(increment, std::ref(foo_count), 
        std::ref(foo_count_mutex), "foo");
    std::thread increment_bar(increment, std::ref(bar_count), 
        std::ref(bar_count_mutex), "bar");
 
    std::thread update_overall([&]() {
        done_mutex.lock();
        while (!done) {
            done_mutex.unlock();
            int result = std::try_lock(foo_count_mutex, bar_count_mutex);
            if (result == -1) {
                overall_count += foo_count + bar_count;
                foo_count = 0;
                bar_count = 0;
                std::cout << "overall: " << overall_count << '\n';
                foo_count_mutex.unlock();
                bar_count_mutex.unlock();
            }
            std::this_thread::sleep_for(std::chrono::seconds(2));
            done_mutex.lock();
        }
        done_mutex.unlock();
    });
 
    increment_foo.join();
    increment_bar.join();
    done_mutex.lock();
    done = true;
    done_mutex.unlock();
    update_overall.join();
 
    std::cout << "Done processing\n"
              << "foo: " << foo_count << '\n'
              << "bar: " << bar_count << '\n'
              << "overall: " << overall_count << '\n';
}

Possible output:

bar: 1
foo: 1
foo: 2
bar: 2
foo: 3
overall: 5
bar: 1
foo: 1
bar: 2
foo: 2
bar: 3
overall: 10
bar: 1
foo: 1
bar: 2
foo: 2
overall: 14
bar: 1
foo: 1
bar: 2
overall: 17
foo: 1
bar: 1
foo: 2
overall: 20
Done processing
foo: 0
bar: 0
overall: 20

[editar] Veja também

(C++11)
bloqueia especificados semáforos, blocos se algum não estão disponíveis
Original:
locks specified mutexes, blocks if any are unavailable
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(modelo de função) [edit]